Glass-grinding machines

ABSTRACT

A glass-grinding machine having a holder for a glass, and a grinding wheel to cut the outer surface of the glass, in which the holder is supported on a vertically disposed spindle, rotatable about and movable along its axis, and the grinding wheel is movable towards and away from the axis. There is means to control the movement of the holder and the grinding wheel, so to cut features on the glass according to a predetermined program.

United States Patent [56] References Cited UNITED STATES PATENTS1,615,978 2/1927 Greer 51/107X 1,635,491 7/1927 Milliken 51/1071,650,375 11/1927 Milliken 51/107 2,171,007 8/1939 Rice 51/107 PrimaryExaminer0thell M. Simpson Att0rneyWatson, Cole, Grindle & Watson 10Claims, 11 Drawing Figs.

US. Cl 51/107, 51/80, 51/92 Int. Cl 1324b 5/00, B24!) 7/00, 82% 7/24Field of Search 51/92, 94, 95, 96, 97, 80, 83, 89, 107

PATENTEDJUN Han 3581.443

SHEET 0k 0F 11 PATENTED JUN 1197! 3.581.443

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PATENTED JUN 1 I971,

SHEET 11 HF 11 GLASS-GRINDING MACHINES The invention relates to grindingapparatus, for example, grinding apparatus for grinding decorativepatterns on glassware.

The various features of the invention include, a device which causes thegrinding wheels to be moved in accordance with a program to followvariations of shape of the glassware, an electric stepping motor forstepwise rotation of the glassware while it is being ground, andautomatic means for feeding the glassware to the apparatus.

The invention provides a glass-grinding machine of the kind comprisingmeans to hold a cylindrical glass with the outer surface or the partthereof to be out free, a grinding wheel rotatable about an axis in aplane parallel to a tangent to the glass or at a small angle thereto,means to rotate the axis of the grinding wheel in the said plane toalter the plane of rotation of the wheel with respect to the axis of theglass, the glass holder and the wheel are relatively movable indirections axially of the glass and towards and away from one another inwhich the holder is supported on a vertically disposed spindle, thegrinding wheel is supported for movement towards and away from the axisof the spindle, there is drive means to rotate and to move the spindleabout and along its axis, and to move the grinding wheel towards andaway from the axis, and there is means to control the drive meaNs inresponse to a predetermined program.

In one formthe 'drive means to move the grinding wheel towards and awayfrom the spindle includes two drive elements arranged to act in series,one of which elements provides a fine control for the pressure withwhich the grinding wheel engages the glass, and the other of whichelements moves the grinding wheel towards and away from the glass tomake successive cuts.

In this form the movement caused by the first element is controlled by afeeler responsive to the shape of the glass or to a template having aprofile corresponding to the shape of the glass.

Preferably there is a conveyor adjacent to or forming part of themachine, which conveyor has an upwardly facing horizontal surface, andthere is means to transfer the holder from its position adjacent thegrinding wheel to a position above the conveyor.

In this form the arrangement is such that the axial movement of thespindle is utilized to engage upwardly facing glasses on the aforesaidsurface of the conveyor.

In this form it is preferred that the holder has means to determinewhether or not a glass is secured thereto, which means is arranged toprevent movement of the holder from its position above the conveyor if aglass is not secured thereto.

There is preferably means to alter the plane of the grinding wheel withrespect to the axis of the glass while a cutting operation is inprogress.

In one form the control means include means responsive to the movementof the spindle and the grinding wheel, means to compare the output ofthe responsive means with predetermined values, and means to activatethe drive means to bring the moving elements to predetermined positionscorrespond ing to the predetermined values.

In this form the output from the responsive means is applied to a seriesof relays which lock the machine against cutting action until all movingelements are correctly positioned.

Alternatively or additionally the responsive means comprise transducersconnected to stepping motors each arranged to drive a magnet past aplurality of magnetic reed switches.

The various features are present in specific forms in the followingexamples of a grinding machine and a modification thereof, which willnow be described, by way of example only, and with reference to theaccompanying drawings, in which:

FIG. 1 shows a side view of part of the apparatus;

FIG. 2 shows a front view ofpart of the two grinding heads;

FIG. 3 shows a plan view of parts of the two grinding heads;

FIG. 4 shows, in diagrammatic form, control apparatus for controllingthe movement of the grinding heads so that they follow the contour ofthe glassware;

FIG. 5 shows an end view of part of the vacuum apparatus;

FIG. 6 shows a plan view of part of the vacuum apparatus;

FIGS. 7a through 7d show, in diagrammatic form, various positions ofpart of the apparatus controlling rotation of the glassware and therelative positions of a tumbler for each position of the controllingapparatus;

FIG. 8 shows an electrical circuit used in the apparatus;

FIG. 9 shows a front view ofa modified version of one of the grindingheads shown in FIG. 2;

FIG. It) shows an end view of a modified version of the apparatus shownin FIG. 5; and

FIG. 11 shows a modified control system.

This embodiment of the invention provides a grinding machine whichgrinds in the surface of, for example, a glass tumbler, a pattern ofsurface cuts to produce what is generally known as a cut glass tumbler.Many of the traditional cut glass patterns are of crisscross form whichrequires cutting the tumbler at an angle to the axis of the tumbler intwo directions. The tumbler is indicated in the drawings by referencenumeral 10.

The grinding machine comprises a main stand 11, comprising a lower part12, an upper part 13 and an intermediate part 14 joining one side of theupper part to the same side of the lower part, thereby forming a Gshaped main stand 11. Mounted above the lower part 12 is the grindingunit 16 and mounted inside and below the upper part 13 is the vacuumapparatus 17 for holding the tumbler. A conveyor belt 18 is mounted topass adjacent the intermediate part 14 between the upper and lower partsof the main stand. A contour following apparatus is provided forcontrolling the movement of the grinding unit and the vacuum apparatusin accordance with the contours of the tumbler.

The grinding unit 16 (FIGS. 1, 2 and 3) comprises two similar grindingheads 21 and 22 facing one another. One head 21 will be described,similar parts of the other head 22 being numbered on the Figuressimilarly but with the suffix a. The head 21 is mounted on a screwjack23 attached to the bottom part 12 of the main stand 11. The head 21comprises a table 24 attached to the screw of the screwjack 23. Thescrewjack may be rotated to vary the height of the table 24, the screwbeing locked in position by two locknuts 26. A further upper table 27 issituated adjacent and above the lower table 24 and is adjustable forlimited rotation (in the plane of the faces of the tables) relative tothe lower table 24. Slots 28 are cut in the upper table 27 so thatclamping members may be passed through the upper table 27 to clamp theupper and lower tables 27 and 24 together. Mounted on the upper tableare a pair of abutments 32 and 33. A pair of slide rails 29 are mountedbetween the abutments 32 and 33 and a slide member 31 is slidablymounted on the rails 29. The slide member 31 comprises a piston unit 34which includes a closed cylinder attached to the slide member 31. Apiston is situated within the cylinder. The piston is attached bymembers passing through the ends of the closed cylinder to the abutments32 and 33. If hydraulic fluid under pressure is introduced into thecylinder on one side of the piston the slide member 31 moves one wayalong the rail 29 and if hydraulic fluid is supplied under pressure tothe other side of the piston the slide member 31 moves the opposite wayalong rail 29.

Mounted on and above the slide member 31 is a platform 37 on twoopposite sides of which are mounted supports 38 and 39 the support 39being on the side of the platform 37 closest to the other grinding head22. Rotatably mounted between the supports 38 and 39 is an axle 41 whichpasses through the support 39 and projects towards the other grindinghead 22. Solidly mounted around the axle 41 between the supports 38 and39 is a cogwheel 42. A rack 43 is slidably mounted on platform 37 sothat the rack 43 engages the cogwheel 42. A hydraulic ram 44, one end ofwhich is attached to the rack 43 and the other end of which is attachedto the platform 37 may be operated to move the rack 43 and hence rotatethe axle 41 through the cogwheel 42. A plate 46 is attached to the partof the axle 41 which projects beyond support 39 towards the othergrinding head, the plate 46 extending transversely of the axis of axle41. A support plate 47 extends from plate 46 substantially parallel to,but displaced from the axis of axle 41, towards the other grinding head22. Passing through the end of this plate 47 is an axle 48 which isrotated by a motor 49 attached to the plate 47. A grinding wheel 51 issolidly mounted on the other end of the axle 48. The center part of thegrinding wheel 51, (about which it is rotated by the axle 48) and thepoint of contact of the grinding wheel 51 with the glassware beingground, are both situated on the line of the axis of axle 41. Thus, asthe axle 41 is rotated by the ram 44, point of contact of the grindingwheel on the glass does not change. The grinding wheel 51 comprises aflat disc, the cross section of the edge of which tapers usually in theshape of a 'V to a point 52. Thus the edge of the grinding wheel whichhas a diamondcutting surface produces a V shaped cut in the surface ofthe tumbler. As previously stated, the two grinding heads 21 and 22 aresimilar. The motors 49 and 49a, being on opposite sides of theirassociated plates 47 do not cause the motors 49 and 49a to come intocontact with each other during any rotation of the tables 27 and 27a.

The vacuum apparatus 17 is shown in FIGS. and 6. Extending downwardlyfrom the upper part 13 of the main stand 11 there is a spindle 56 (seeFIG. 1 also) to the bottom end of which is attached a vacuum chuck 57.The vacuum chuck 57 comprises a thick circular plate 58 the outer edgeof which provides a frustoconically shaped face 59 the thicker part ofthe frustoconical shape being above the narrower part. A vacuum passage61 passes through the spindle 56 and plate 58 to an aperture 62 in theundersurface of the plate 58. The spindle 56 is rotatably mounted in abearing block 63. A plate 64 is mounted on the upper end of the spindle56 such that the plate does not rotate with the spindle 56 but movesaxially with the spindle 56. An electric stepping motor 66 is mounted onplate 64 and rotates spindle 56 through a reduction gear train 67. Theoverall ratio of the reduction gear train is between 25:1 .and 75:1. Aram 65, including an hydraulic cylinder 68 is attached to the bearingblock 63 with the axis of the cylinder parallel to the axis of thespindle 56. The piston of the cylinder 68 is attached to the plate 64.Operation of the hydraulic ram 65 causes the plate 64 and hence thespindle 56 to move up and down relative to the bearing block 63. Thebearing block 63 is mounted on a horizontal slide 69 which is attachedby support beams 71 to the upper part 13 of the main stand 11, sothatthe bearing block may move towards and away from the intermediate part14 of the main stand 11. The bearing block 63 is moved along the slide69 by a horizontally mounted hydraulic ram 72. Thus the ram 72 moves thevacuum chuck 57 between one position where the vacuum chuck is above theconveyor belt 18 and another position in which the vacuum chuck is abovethe grinding wheels 51 and 51a.

The contour following apparatus is shown in FIGS. 4 and 5. A mount 73 isattached to the plate 64 and has removably mounted on it a flat template74, the edge 75 of which corresponds to the outline of the glassware, inthis case, a tumbler or wineglass 10, which is to be cut. An hydrauliccylinder 76 is mounted rigidly relative to the bearing block 63, thepiston 77 of the hydraulic cylinder 76 abutting the edge 75 of thetemplate 74. Thus as the spindle 56 moves up and down, the template 74moves with it, thereby pushing in and out the piston 77. A slavehydraulic cylinder 78 mounted on table 27 moves its piston 79 in and outin synchronism with piston 77. Attached to the other end of piston 79 isa microswitch 81 the lever 80, of which abuts part of the slide member31. The microswitch 81 controls the supply of fluid to the piston units34, so that the projecting part of the slide member 31 is alwaysadjacent the microswitch. The supply of fluid to the piston units 34aand 36a of the grinding head 22 is also controlled by the microswitch 81and hence both of the grinding wheels 51 and 51a move towards and awayfrom the tumbler in synchronism with the movement of piston 77 Thegrinding machine operates as follows. The glass tumblers which are to beout are placed on the conveyor belt 18 with their open ends facingupwards. Successive tumblers are placed a set distance apart from oneanother and in a set position along the belt 18. The belt 18 moves thetumblers intermittently under the upper part 13 of the main stand 11.When a tumbler reaches the required position, the belt 18 stops. Thespindle 56 is moved over the belt 18 by the contraction of the hydraulicram 72. The spindle 56 is then lowered by expansion of the hydraulic ram65 until the vacuum chuck 57 abuts the tumbler standing below. The sizeof the plate 58 on the chuck 57 is chosen so that the rim of the tumblerabuts the conical face 59 of the plate 58 everywhere around itscircumference. The air within the tumbler is then withdrawn along thevacuum passage 61 and the tumbler thereby adheres to the chuck 57. Thehydraulic ram 65 then raises the spindle 56 and chuck 57. When the chuckhas moved a short distance a vacuum sensing device is switched on totest that there is a vacuum in passage 61. If there is little or novacuum, then air must be entering the vacuum passage 61. This meanseither that the tumbler rim is not firmly sealed against the conicalface 59 of the plate 58 or else the tumbler has not been picked up. Thusif little or no vacuum is detected, the ram 65 is reversed to lower thechuck S7 to try again to pick up the tumbler or to grip the tumbler morefirmly held on the chuck 57. This process is repeated until sufficientvacuum is detected. When there is sufficient vacuum, the chuck continuesto move upwards since this means that the tumbler is firmly secured tothe chuck 57.

When the hydraulic ram 65 has lifted up the spindle 56 sufficiently,hydraulic ram 72 extends to move the spindle, chuck and tumbler towardsthe grinding wheels 51 and 51a. At this stage, the grinding heads 21 and22 are spaced well apart from one another so that the tumbler may enterbetween the grinding wheels to the position in which it is to be cut,hereinafter called the operating position. The table 27 has previouslybeen manually rotated relative to the table 24, the axis of thisrotation passing vertically through the operating position, so that thegrinding wheels are in the necessary relative positions for a particularstyle of tumbler or glassware. The grinding wheels have previously beenrotated to the required angle relative to the tumbler by movement of therack 43.

When the tumbler is in the operating position hydraulic fluid atrelatively high pressure is applied to the piston unit 34 and 34a andthe slide members 31 and 31a move the grinding wheels rapidly towardsthe tumbler. However, the piston 77 of hydraulic cylinder 76 contactsthe edge of template 74 and is stopped just before the grinding wheelsreach the tumbler and thus the forward motion of the slide members 31and 31a is checked. There is, however, a further low pressure supply ofhydraulic fluid supplied to the piston units 34 and 34a to move themslowly forward so that the grinding wheels touch the glass relativelyslowly. The rapid movement of the grinding wheels towards the tumblerreduces the total time the tumbler is in the grinding machine. The twogrinding wheels are rotated by hydraulic motors 49 before they contactthe tumbler. The grinding wheels both contact the tumbler and cut thesurface of the tumbler simultaneously. The grinding pressure i.e. thepressure exerted by the grinding wheels on the tumbler, is provided bythe low pressure supply of hydraulic fluid to the piston units 34 and34a.

To produce a line cut the tumbler is moved by movement of the steppingmotor 66 and hydraulic ram 65. Since the tumbler is not normallycylindrical the diameter of the tumbler changes at the point of contactof the grinding wheels as the grinding wheels move up and down thesurface of the tumbler. Since the piston 76 is also moving up and downthe template 74 in unison with the grinding wheels the grinding wheelsare thereby moved in and out relative to the cutting position tocompensate for these changes of diameter by the slave hydraulic cylinder78 and microswitch 81.

To produce a spaced crisscross pattern of diagonal cuts on the tumbler,the grinding wheels are rotated by the rack 43 to the required angle andthe first cut made by each grinding wheel. This involves the steppingmotor 66 rotating the tumbler a fixed distance. If the diagonal cuts areto be relatively close to one another, the stepping motor 66 must thenrotate the tumbler backwards (when the grinding wheels are clear of thetumbler) a fixed distance. The process is then repeated. The method ofcontrolling the stepping motor 66 to perform this operationautomatically will be described later in the specification. When all ofthe cuts in one direction are complete (since there are two grindingwheels, this will be after half a revolution of the tumbler), thegrinding wheels are rotated by the rack 43 to the angle required toproduce the other set of diagonal lines in the pattern.

When the required pattern has been cut on the tumbler, the tumbler ismoved back onto the belt 18 by operation of the ram 65 and ram 72. Whenthe tumbler has reached the conveyor belt 18, the vacuum is released inthe vacuum chuck 57. To ensure that the tumbler is dislodged from thechuck, low pressure air is blown through pipe 61. A pressure sensitiveswitch 132 will prevent the machine continuing to cycle until a drop inpressure indicates the tumbler has been released. The belt then movesforward so that the next tumbler on the belt may be picked up by thevacuum chuck 57.

When different glassware is to be cut, for example, wineglasses, atemplate corresponding to this glassware is mounted on the mount 73.

The method of controlling the stepping motor 66 to cut a spiral grooveon the tumbler will now be described with reference to FIGS. 7a-d. Thestepping motor 66 rotates the tumbler during the cutting stroke and atthe same time the hydraulic ram 76 moves it linearly along the line ofthe tumbler axis. These two motions, compounded, twist the tumblerdiagonally or helically between the grinding wheels 51, 5111. A furtherstepping motor 91 (FIG. 8) is controlled to rotate an arm 86 at the samerate as the stepping motor 66 rotates the tumbler 10. Spaced around thearc swept out by the arm 86 are three switches 87, 88 and 89. The arm 86is initially adjacent the switch 87 (FIG. 7a). When the cutting of adiagonal line on the tumbler begins, the stepping motor 66 and the otherstepping motor 91 rotate the tumbler and the arm 86 (clockwise in FIG.7) in synchronism with each other. The rotational position of the switch89 is adjusted so that when the tumbler has been rotated to produce therequired cut, the arm 86 reaches the switch 89 (FIG. 7b). The arm 86then switches off and switch 89 which reverses the direction of motionof the stepping motors 66 and 91. The closing of the switch 89 alsocontrols the hydraulic valves that actuate the rams 34, 34a and 65 sothat the grinding wheels withdraw from the glass and it is lifted up toits original position. Thus the tumbler rotates backwards (the indexingstroke) in synchronism with the backwards rotation of the arm 86. Whenthe arm 86 reaches switch 88 on this backward rotation, (FIG. 70) theswitch 88 is operated which thereby cuts off pulses to the steppingmotor 66 which stops rotation of the tumbler. However, the arm continuesto be rotated backwards by the motor 91 until it reaches the switch 87(FIG. 7d) which reverses the stepping motor 91 and starts the motor 66.The operation then repeats itself. During this operation the tumbler hasbeen moved forward by a first angle, and backwards by a second angle,the second angle being smaller than the first angle. The diagonal cutson the tumbler are therefore displaced by a distance y (FlG. 7d)relative to one another and the two angles and hence the distance y" canbe altered by moving the switches 88 and 89 around the arc swept out bythe arm 86. Movement of the switch 89 around the arc varies the lengthof the diagonal cut on the tumbler.

An electrical circuit is required to operate the stepping motors andvarious other parts of the apparatus and the method of operation of theelectrical circuit will now be described with reference to FIG. 8. Inthis diagram the following switches are biassed towards an openposition, 101, 104, 106, 109,87, 88, 89, 124, 127, 131 and 132. Switches108, 89 and 134 are biassed to a closed position.

The switch 101 is momentarily closed to start the operation of themachine. The closure of the switch 101 allows the voltage on input lineto be connected to relay 102. Both relays 102 and 111 (see later) are ofthe kind which are flipped from one state (in which the relay connectsthe input to one output) to a second state (in which the relay connectsthe input to a second output) by a voltage pulse. The voltage on line100 thereby switches the relay 102 to a position in which it provides anoutput along line 103 to the valve controlling the input to cylinder 68.This causes the cylinder 68 to extend and lower the chuck 57 onto thetumbler and vacuum is applied along vacuum passage 61. When the chuckreaches the tumbler it closes switch 104. This operates relay 107 byapplying voltage from line 100 through closed switch 108 and switch 104.The operation of relay 107 reverses the direction of ram 65. To ensurethat the tumbler :is correctly seated on the chuck a vacuum-sensingdevice is incorporated in the circuit. This consists of switch 108 whichis. opened by the chuck when it has been raised some 3 inches above thebelt and switch 106 which is an aneroid-type switch closing when thevacuum in the vacuum chuck reaches a certain level. If the tumbler isincorrectly held, or not held at all, the vacuum will have dropped belowa certain level and switch 106 will be open. Thus on opening switch 108,no voltage is applied via switch 104 to control relay 107 whichtherefore changes to its other state, thereby reversing thevalve-controlling cylinder 68. Thus the motion of the piston in cylinder68 is reversed so that the vacuum chuck is lowered and the process isrepeated. The vacuum chuck will not lift any higher than switch 108allows it to until the tumbler is firmly adhering to the vacuum chuck.

When the vacuum sensing switch 106 and switch 108 indicate that theglass is firmly adhering to the vacuum chuck, the ram 65 contracts toraise the vacuum chuck fully. When the vacuum chuck is fully raised itmomentarily closes switch 109. This switches relay 102 which in turnswitches relay 111 to a position in which the input on line 112 is fedto line 113 which operates a valve to extend! ram 72. The tumbler isthereby moved to the grinding position.

When the tumbler reaches the grinding position, the switch 114 isswitched to a second position in which it cuts off the supply to thepart of the electrical circuit so far described. The input line 100 isthen connected to line 116. The momentary closing of switch 87 initiatesthe cutting cycle by l. passing the input voltage along line 117 to avalve which extends the ram 65.

ll. changing the relay 118 to the position in FIG. 8 in which no signalis passed along line 119 to the valve controlling the piston units 34and 34a. In this case the spring loaded valve operates the piston unitsto move them inwards so that the grinding wheels move in towards thetumbler.

lll. changing the relay 118 to the position in FIG. 8 which starts bothof the stepping motors 66 and 91.

The relay 118 when in the position shown in FIG. 8 is held in thatposition since voltage is applied along line to the relay control lineeven when switch 87 is open.

The stepping motors 66 and 91 are fed by pulses by an oscillator 121.The pulses are fed to the two stepping motors through amplifiers andpulse shapers and provision can be made for counting these pulses inorder to achieve a form of numerical control over the machine. Theoscillator has two outputs one of a fast rate of pulses and one of aslow rate of pulses for rapid and slow rotation of the spindle. Thestepping motors work at two speeds, a relatively slow speed during thecutting stroke and a relatively fast speed during the indexing stroke tominimize the time the machine is not actually cutting the tumbler. Thefast pulse rate is passed along line and the slow rate which gives theslow variable speed for cutting along line 122. The relay 118 controlswhich rate is fed to the stepping motors.

Switch 124 is provided to prevent: the tumbler, when it is in thegrinding position, being moved by the ram 65 before the grinding wheelshave engaged the tumbler. This prevents skid marks at the start of eachcutting stroke.

When the switch 89 is momentarily opened a voltage is applied to relaycontrol line 115 and thus relay 118 changes to its second position. Thiscauses voltage to be applied to the valve controlling the piston units34 and 34a which thereby removes the grinding wheels from the tumbler,the speed of the stepping motors is changed (this is controlled by theposition of relay 118), and the direction of rotation of both steppingmotors is reversed. When switch 88 is closed by the returning arm 86 isoperates relay 126 which switches off the pulses being fed to motor 66.When the vacuum chuck has completed a complete half cycle, (i.e. thetumbler has been rotated through 180) switch 127 is tripped closed whichthen changes relay 128..This relay then operates via line 129 and avalve controlling the hydraulic ram 64 changes the angle of the grindingwheels. The relay 128 also reverses connections 122 and 125 reversingthe stepping motors.

When the complete pattern has been cut on the tumbler, switch 131 isautomatically closed. This operates via line 113 the valve to contractthe ram 72. Thus the vacuum chuck is moved away from the grinding wheelsto a position above the belt. Switch 114 is then tripped to switch over.When the chuck reaches the belt, switch 109 is momentarily closed andthus the ram 65 is moved downwards since the closure of switch 109alters relay 102 to pass a voltage along line 103. When the tumblerreaches the belt, the ram 65 is reversed and the vacuum turned offallowing low pressure air to pass through the vacuum piping to thevacuum chuck. If the tumbler does not fall off the chuck, air pressurewill build up in the vacuum line and this will close the pressuresensitive switch 132. As before, switch 108 opens on the upward strokeof the vacuum chuck, and, if an excess air pressure indicates that thetumbler has not been ejected, by switch 132 remaining open the relay 107is changed so that the vacuum chuck returns to the belt. When thetumbler has been ejected the ram 65 lifts the chuck to its uppermostposition. Switch 109 is again tripped which changes relay 102 so thatrelay 105 is changed. Thus a voltage pulse is passed onto line 133 whichcauses the conveyor belt 18 to move forward so that a new tumbler isplaced beneath the vacuum chuck.

In automatic working of this grinding machine, the belt moving forwardmay close switch 134 thereby initiating the cycle again. Thus, once thestart switch 101 has been closed operation of the grinding machine iscompletely automatic.

A manual switch, 133, is incorporated in this circuit to allow themachine to perform spot cuts e.g. the tumbler is not moved at all duringcutting. This switch 135 simply breaks the connection between the line122 and stepping motor 66.

In this case a timer must be incorporated to obtain the same depth ofcut each time.

The invention is not restricted to details of the foregoing example. Forexample, different size chucks may be used for different size tumblersand for other glassware. Also the grinding machine may be used to givecuts along the axis of the tumbler.

A further stepping motor operating a lead screw may be used to replaceram 65.

A pulse shaper may be included between the oscillator 121 and thestepping motors.

Several grinding machines may be linked in series, one machine cutting,say, the foot of a wineglass, and another the bowl of the wineglass.

A disc brake may be provided on plates 46 to lock it firmly in positionduring cutting to prevent vibration of the grinding wheels.

An alternative method of cutting a groove of equal depth in the wall ofa curved tumbler is as follows: Instead of employing a template of theshape of the tumbler to be followed for varying the position of theslide members 31 and 31a, a feeler placed near the tip of the grindingwheel senses alterations in shape of the tumbler and transmits any suchvariation to the slide members. To avoid scratching the glass the feelercan take the form ofa low pressure air pipe. Any build up of pressure inthis pipe (which would result when its tip came close to the surface ofthe tumbler) switches the hydraulic valve controlling the hydraulic rams34 and 34a and these move the slide members into or away from thetumbler as required. If two such air sensors were used, one to each sidemember, the machine could cut irregularly shaped glassware, for example,wineglasses with bent stems.

In FIG. 9 there is a fixed table 201 which is rigidly mounted on theframe. This arrangement differs from that shown in FIG. 2 in that thescrewjack and swingable upper table are eliminated. The table supports afixed abutment 202 which holds a central part of a piston unit 203. Atthe ends of the piston unit there are downwardly extending arms 204 and205 which are attached to the ends of a mounting plate 206. The plate206 is thus movable in response to the movement of the piston unit 203,which is arranged to move the guiding wheel towards and away from theglass.

The plate 206 supports two further arms 207 and 208 which hold the endsof a high pressure cylinder 209. The cylinder 209 has a hollow piston210 to which a grinding wheel (not shown) is attached. The power andfluid supplied to the grinding wheel are fed through the hollow piston.The end of the piston 210 away from the grinding wheel is connectedthrough a flexible coupling 21] to a gear box 212. A motor (not shown)is arranged to rotate the piston 210 through the gear box 212, thusreplacing the rack and cog wheel 43 and 42 respectively of FIG. 2. Thisprovides angular adjustment for the plane of the grinding wheel.

The high pressure cylinder 209 is operable to withdraw the grindingwheel from the glass between successive cuts, and the piston unit 203 isoperable as an air spring in response to feeler means 77 which followsthe profile of the glass being cut. The piston unit 203 thus controlsthe depth of the cut made on the surface of the glass.

A modified glass-raising device is shown in FIG. 10. In this device twofixed sidewalls 231 and 232 support guide rails 233 and 234respectively; each guide rail has upper and lower running surfaces. Acarriage 235 is mounted on rollers 236- 237 which engage the runningsurfaces of the guide rails 233 and 234. The carriage 235 is formed of acylinder 246 and an upright guide 245. The cylinder surrounds a ram (notshown) which is mounted on a spindle 238 to the lower end of which aglass 10 may be attached. At the upper end of the spindle there is agearbox 239 and a motor 240. The motor is arranged to drive the gearboxthrough a flexible coupling 24], and so to rotate the spindle 238. Thegear box 239 has guide wheels 242 and 243 which engage the upright guide237 to resist rotation of the motor 240 about the spindle. The spindle238 is hollow to receive the vacuum line to secure the glass.

A revised control system will now be described with reference to FIG.11. This system includes sensors or transducers on the elements of themachine that move the glass holder or the grinding wheel. These elementsmay be termed glass raise, glass rotate, wheel angle", and wheel infeed.

The movement elements in this example are illustrated as follows. Theglass raise" is provided by the ram 68, or the ram in the cylinder 246,which raises and lowers the glass. The glass rotate" is provided by themotor 66 or the motor 240 which rotates the glass. The wheel angle"element is provided by the ram 44, or the motor driving the gearbox 212,which elements rotate the grinding wheel about an axis in its plane ofrotation and passing through the axis of the spindle. The wheel infeedelement may be a hydraulic ram to index the wheel into and away from theglass and an air spring to control the grinding pressure. This is givenas the pistons 203 and 209 which move the grinding wheel towards andaway from the glass. In FIG. 11 the glass raise sensor or transducer isdesignated 300 and the glass rotate sensor or transducer is designated301.

Each transducer produces a train of impulses, the number of impulsesbeing proportional to the movement of the element, and these are fedinto stepping motors causing them to rotate. There is one motor to eachelement and the angular displacement of its rotor is proportional to themovement of that element.

Each motor has a magnet fitted to an arm on its rotor and so this magnetsweeps around an arc of a circle as the element moves. A ring of reedswitches is packed around this circle so that the switch that is nearestto the rotor arm is closed by the magnet. There are as many suchswitches as there are steps to a complete revolution of the steppingmotor. In this instance, the motor used has 48 steps to a revolution andsuch a motor, with its attendant ring of reed switches, acts as a 48 wayselector switch.

In any subsequence of the cutting operation in which a cut is formed, apair of reed switches will be selected on each of these stepping motorarrays. The first switch of each pair (called the a" switch on thediagram) dictates the position its element should take up at the startof the cutting stroke, c.g. it controls the indexing movement of theelement between cuts. Similarly, the second switch (b) dictates themovement of its particular element during cutting.

The signals from the a" and b switches are fed into a series ofinterlocking relays 303. These determine that all the elements havecompleted their indexing stroke before cutting begins. At the end of thecutting stroke only one b" signal is used to switch to the nextsubsequence. This prevents damage to the grinding wheel through oneelement stopping prematurely.

The positions of each element that are controlled during a subsequenceareas has already been stated-dictated by the pair of switches selectedon each stepping motor array. A new pair of switches is selected for thedifferent subsequences and this is done by a programming uniselector302. However, as most out decorations are made up of a relatively fewnumber of similar cuts, repeated many times, this programminguniselector is linked with a second uniselector 304 that controls a stepand repeat function. This allows up to 50 similar cuts to be made on theglass at one single program station.

Not every program station controls a cutting operation. The firststation controls the pickup of a glass from the feed belt and the lastcontrols the ejection of a cut glass onto this same belt.

This is done by controlling the glass raise element 72 or 236 only andinterlocking the signals its stepping motor array produces with thosefrom four limit switches. These are designated with reference to thefirst embodiment:

I at the take-out position on ram 72 1 on a pressure sensitive switchattached to the vacuum pipe 61 which leads to the chuck holding theglass 1 a vacuum sensitive switch on the same pipe, 61

1 on the feed belt, which signals when a fresh glass is correctlypositioned beneath the chuck.

On the glass eject sequence at the end of the cutting operations ram 72is signalled to withdraw the glass holding spindle shown in FIG. 5 fromthe grinding position to a point above the feed belt. At the same time,this glass hold actuator is extended so that the glass is 1 inch abovethe belt.

When both these two movements are complete, e.g., switch 1 on the ram 72and a on the glass raise stepping motor array are both closed, thevacuum applied to the chuck is turned off and low pressure air isinjected into pipe 61. This blows the glass off the chuck onto the belt.When the glass is released, there will be a fall in pressure in pipe 61which will be sensed by 1 This signals the machine to turn itself offand also signals the uniselectors to return to their zero position.

However, for fully automatic operation, this signal can be diverted fromswitching off the controller to moving the feed belt until a new glassis presented to the chuck. l then switches vacuum back into pipe 61 andlowers 68 until the chuck engages with the rim of the glass. It thenhalts until 1 on the vacuum sensor indicates that the glass is finnlyattached to the chuck. 68 then lifts the glass off the belt and 72extends to the grinding position where the grinding cycle is repeated.

Should the vacuum fail at any time during the cutting operation-and thiswould indicate either that the glass has become unseated on the chuck orthat is has broken-the program will be cancelled and this last movementwill be reversed, bringing the chuck back to the belt.

lClaim:

l. A glass-grinding machine of the kind comprising means to hold a glassso that a portion of its outer surface may be cut unobstructed, agrinding wheel rotatable about an axis in a plane parallel to a tangentto the glass or at a small angle thereto, means to rotate the axis ofsaid grinding wheel in said plane to alter the plane of rotation of saidwheel with respect to the axis of the glass, a vertically disposedaxially movable spindle arranged to support said glass-holding means,linear bearing means to support said grinding wheel for movement towardand away from the axis of said spindle, whereby said glass holder andsaid grinding wheel are relatively movable in directions axially of theglass and toward and away from one another drive means provided torotate said spindle about its axis, drive means provided to move saidspindle vertically along its axis, drive means provided to move saidgrinding wheel linearly toward and away from said spindle axis, andmeans provided to control each of said drive means in response to apredetermined program.

2. A machine as claimed in claim 1 in which said drive means to movesaid grinding wheel linearly toward and away from said spindle axisincludes two drive elements arranged to act in series, one of saidelements providing a fine control for controlling the pressure withwhich said grinding wheel engages the glass, the other of said elementsmoving said grinding wheel toward and away from the glass to makesuccessive cuts.

3. A machine as claimed in claim 2 in which the movement caused by saidone element is controlled by a feeler responsive to a template having aprofile corresponding to the shape of the glass.

4. A machine as claimed in claim 1 wherein a conveyor is providedadjacent to the machine, said conveyor having an upwardly facinghorizontal surface, and there being means provided to transfer saidholder from its position adjacent said grinding wheel to a positionabove said conveyor.

5. A machine as claimed in claim 4 in which the axial movement of saidspindle is effective to engage upwardly facing glasses resting on saidconveyor surface.

6. A machine as claimed in claim 5 in which said holder has means todetermine whether a glass is secured thereto, said determinative meanscomprising an electric circuit arranged to prevent movement of saidholder from its position above said conveyor if a glass is not securedthereto.

7. A machine as claimed in claim 1 further including a geared motor toalter said plane of the grinding wheel with respect to the axis of theglass while a cutting operation is in progress.

8. A machine as claimed in claim 1 in which said control means includeelectrical circuits responsive to the rotary and linear movements ofsaid spindle supporting said glass holder and also of the linearmovements of said grinding wheel, as it is fed into and disengaged fromthe glass, said circuits comparing these movements with predeterminedvalues programmed into the machine.

9. A machine as claimed in claim 8 in which the output from said controlmeans is applied through a series of relays which lock the machineagainst cutting action until all moving elements are correctlypositioned and a glass securely held on said holder.

10. A machine as claimed in claim 8 in which the responsive electriccircuits comprise transducers connected to stepping motors each arrangedto drive a magnet past a plurality of magnetic reed switches.

1. A glass-grinding machine of the kind comprising means to holD a glassso that a portion of its outer surface may be cut unobstructed, agrinding wheel rotatable about an axis in a plane parallel to a tangentto the glass or at a small angle thereto, means to rotate the axis ofsaid grinding wheel in said plane to alter the plane of rotation of saidwheel with respect to the axis of the glass, a vertically disposedaxially movable spindle arranged to support said glass-holding means,linear bearing means to support said grinding wheel for movement towardand away from the axis of said spindle, whereby said glass holder andsaid grinding wheel are relatively movable in directions axially of theglass and toward and away from one another drive means provided torotate said spindle about its axis, drive means provided to move saidspindle vertically along its axis, drive means provided to move saidgrinding wheel linearly toward and away from said spindle axis, andmeans provided to control each of said drive means in response to apredetermined program.
 2. A machine as claimed in claim 1 in which saiddrive means to move said grinding wheel linearly toward and away fromsaid spindle axis includes two drive elements arranged to act in series,one of said elements providing a fine control for controlling thepressure with which said grinding wheel engages the glass, the other ofsaid elements moving said grinding wheel toward and away from the glassto make successive cuts.
 3. A machine as claimed in claim 2 in which themovement caused by said one element is controlled by a feeler responsiveto a template having a profile corresponding to the shape of the glass.4. A machine as claimed in claim 1 wherein a conveyor is providedadjacent to the machine, said conveyor having an upwardly facinghorizontal surface, and there being means provided to transfer saidholder from its position adjacent said grinding wheel to a positionabove said conveyor.
 5. A machine as claimed in claim 4 in which theaxial movement of said spindle is effective to engage upwardly facingglasses resting on said conveyor surface.
 6. A machine as claimed inclaim 5 in which said holder has means to determine whether a glass issecured thereto, said determinative means comprising an electric circuitarranged to prevent movement of said holder from its position above saidconveyor if a glass is not secured thereto.
 7. A machine as claimed inclaim 1 further including a geared motor to alter said plane of thegrinding wheel with respect to the axis of the glass while a cuttingoperation is in progress.
 8. A machine as claimed in claim 1 in whichsaid control means include electrical circuits responsive to the rotaryand linear movements of said spindle supporting said glass holder andalso of the linear movements of said grinding wheel, as it is fed intoand disengaged from the glass, said circuits comparing these movementswith predetermined values programmed into the machine.
 9. A machine asclaimed in claim 8 in which the output from said control means isapplied through a series of relays which lock the machine againstcutting action until all moving elements are correctly positioned and aglass securely held on said holder.
 10. A machine as claimed in claim 8in which the responsive electric circuits comprise transducers connectedto stepping motors each arranged to drive a magnet past a plurality ofmagnetic reed switches.